Predictions of ²²⁵Ac and ²²³Ra production cross sections from p, α and heavy ion irradiated thorium and uranium targets

Area of Science:

• Nuclear Physics
• Radiochemistry
• Isotope Production

Background:

• Direct production of Actinium-225 (Ac-225) using proton bombardment of Thorium-232 (Th-232) results in Actinium-227 (Ac-227) impurities, complicating purification.
• Ac-225 can be obtained with higher purity via its parent isotope, Radium-225 (Ra-225).
• Current methods for producing Ra-225 have low cross-sections, necessitating research into more efficient production pathways.

Purpose of the Study:

• To investigate and compare the production cross-sections of Ac-225, Ra-225, Radium-223 (Ra-223), and Thorium-227 (Th-227) using various incident particles and targets.
• To evaluate the feasibility of different production routes for high-purity Ac-225, focusing on Ra-225 generation.
• To identify optimal conditions for maximizing isotope production yields, particularly for Ra-225 and Ac-225.

Main Methods:

• Utilized Monte Carlo transport codes FLUKA and PHITS to simulate nuclear reactions.
• Calculated production cross-sections for Ac-225, Ra-225, Ra-223, and Th-227 by bombarding Th-232 and natural uranium targets.
• Investigated the effects of incident particles (protons, alpha particles, Beryllium-9, Carbon-12) and energies (10-800 MeV/u) on isotope yields.

Main Results:

• Alpha particle and heavy ion bombardment exhibit lower energy thresholds and significantly increased production cross-sections for Ac-225, Ra-225, and Ra-223 compared to proton bombardment.
• Peak production cross-sections for these isotopes are predominantly observed below 100 MeV/u.
• Simulations suggest that alpha particle bombardment of thorium targets is an efficient pathway for producing Ra-225 and subsequently high-purity Ac-225.
• Alpha particle bombardment of natural uranium targets shows a higher predicted Ra-225 cross-section than thorium targets below 100 MeV/u, indicating a potential new production method.

Conclusions:

• Alpha particle bombardment of natural uranium targets presents a promising and potentially more efficient method for producing Ac-225.
• Optimizing alpha particle energy below 100 MeV/u is key for maximizing Ra-225 production yields from natural uranium.
• This theoretical study provides valuable data for guiding future experimental measurements and optimizing Ac-225 production strategies.